I know this feature is experimental but thought you would still want to know about issues.
With the new virtual keyboard added in 4.16, when you focus a textbox it brings u the keyboard correctly, but if you hit back and close the keyboard, the textbox stays focused. Tapping the textbox again does not bring up the keyboard so you have to move focus somewhere else in order to bring up the keyboard.
In most cases this would be a minor issue, but in our case, tapping anywhere else to change the focus restarts the game and the user looses the chance to enter their high score initials.
The solution would be to either loose focus on the textbox when the keyboard is closed, or simply bring the keyboard up again when the textbox is tapped regardless of focus.
(Also having the functions to detect the keyboard open and close in blueprints would be nice, I could have made it loose focus manually with those.)